﻿<!DOCTYPE html>
<html>

<head>
    <title>iframe page</title>
    <script>
        function test() {
            var file = document.getElementsByName("testUpload")[0].files[0];
            console.log(file instanceof File);
        }
    </script>
</head>

<body>
    <input type="file" name="testUpload" />
    <button onclick="test();">test</button>
</body>

</html>